Study On The Preparation-and-properties Of Transition Metal Doped ZnS Diluted Magnetic Nano-semiconductors

In recent years,Due to use of the electronic charge and spin characteristics at the same time,dilute magnetic semiconductor nanomaterials has a broad application prospects in diverse areas,such as logic devices,spin polarized light emitting diode,spin field-effect transistors,field-emission devices,optical isolator,non-volatile memory devices and quantum computer.ZnS is a typical II-VI direct wide band gap semiconductor material with band gap?3.67eV?and free exciting binding energy?60 meV?,it is a versatile and multifunctional semiconductor material,and possess good piezoelectric,ferromagnetic,photoelectric and photosensitive properties.It can effectively adjust the crystal structure and band structure,then control the optical,magnetic and photocatalytic properties of ZnS by controlling the preparation process,changing the type of doping elements and the doping amount.In this paper,one-dimensional ZnS nanorods were successfully synthesized by hydrothermal method.The influence of transition metal Mn and Ni ion doping on the microstructure,morphology,light absorption properties,magnetic properties and photocatalytic activity of the samples were systematically studied.The main research contents and the results are as follows:Finally,the optimal working parameters were obtained through systematically changing the process parameters of hydrothermal method?including molar ratio of reaction substance,reaction solvent volume ratio,reaction temperature and reaction time?,which is controlled in a reasonable range,thus realize the effective control of the crystal structure,grain size and morphology.The microstructures,morphology and bandgap structure of the prepared samples were characterized by XRD,FESEM and UV-vis,and the effects of different process parameters on the morphology and structure were analyzed.The experiment results show that all samples synthesized by this method possess wurtzite structure.The change of reaction material mole ratio,reaction solvent volume ratio,reaction temperature and reaction time influen have no effect on the crystal structure of the ZnS sample,which have obvious change on their morphology.UV–vis spectra confirmed the best light absorption properties of ZnS with uniform distribution,and the well-crystallized nanorod-like structure.Diluted magnetic semiconductors Zn_1-xNi_xS and Zn_1-xMn_xS with different consistency ratio?x=0,0.01,0.02,0.03,0.05 and 0.07?were successfully synthesized by hydrothermal method using ethylenediamine as a modifier.The microstructure,morphology,optical,and magnetic properties of un-doped and transition metal ions?Mn and Ni?doped ZnS nanocrystals were characterized by X-ray diffraction?XRD?,field emission scanning electron microscopy?FESEM?,high-resolution transmission electron microscopy?HRTEM?and X-ray energy dispersive spectrometry?XEDS?,fourier transform infrared spectroscopy?FT-IR?,ultraviolet-visible spectroscopy?UV-vis?,photoluminescence spectra?PL?and the vibrating sample magnetometer?VSM?,respectively.At the same time,the photocatalytic degradation efficiency of Zn_1-xNi_xS and Zn_1-xMn_xS samples was studied by using RhB aqueous solution as model pollutant under sunlight.The experiment results show that all samples synthesized by this method possess wurtzite structure with good crystallization,no other impurity phase appeared.The morphology of the samples is one-dimensional nanorods and well dispersed.The Mn²⁺ and Ni²⁺ substituted for the lattice site of Zn²⁺ and into the ZnS lattice,meanwhile,the lattice constant and grain size of sample are changed obviously with the increase of the doping concentration.UV–vis spectra reveal the band gap of all Zn1-xMxS?M = Mn and Ni?samples greater than that of bulk ZnS?3.67eV?,and occurs blue shift and red shift phenomenon respectively.The photoluminescence spectra of undoped and doped samples possess the broad blue emission band in the range of 400–650 nm.Compared with pure ZnS,The yellow–orange emission from the Mn²⁺ 3d shell 4T1–6A1 transition and green emission from the Ni²⁺ 3F shell 3T1-3A2 transition can be observed in PL spectra of Zn_1-xNi_xS and Zn_1-xMn_xS nanords at 584 nm and 520 nm,respectively.Magnetic measurements indicated that the undoped ZnS samples is superparamagnetic,whereas a certain amount of?Mn and Ni?doped nanorods have room-temperature ferromagnetism,Indicating that the doping of the transition metal has an enhanced effect on the ferromagnetism of the ZnS nanorods.under ultraviolet light,the Rh B aqueous solution is taken as target degradation to explore the photocatalytic properties of Zn_1-xNi_xS and Zn_1-xMn_xS samples.Experimental results show that the doping of transition metals can improve the separation efficiency of photogenerated electrons and holes,compared with the undoped ZnS nanorod,which improve the photocatalytic efficiency of ZnS samples.